Hydrogen sulfide-modified epoxy resins and flexible laminates therefrom

ABSTRACT

MIXTURES OF THE DIGLYCIDYL ETHERS OF A BISPHENOL SUCH AS BISPHENOL A AND A DIGLYCIDYL ETHER OF AN ALIPHATIC POLYHYDROXYL CONTAINING COMPOUND SUCH AS THE DIGLYCIDYL ETHER O NEOPENTYL GLYCOL ARE MODIFIED WITH HYDROGEN SULFIDE TO PRODUCE EPOXY RESINS WHICH WHEN CURED WITH AN AMINATED POLYGLYCOL ARE USEFUL IN THE PREPARATION OF FLEXIBLE LAMINATES.

United States Patent 3,829,354 HYDROGEN SULFIDE-MODIFIED EPOXY RESINS AND FLEXIBLE LAMINATES THEREFROM James L. Bertram, Lake Jackson, Ross C. Whiteside, Jr., Angleton, and Preston H. Franke, Jr., Lake Jackson, Tex., assignors to The Dow Chemical Company, Midland, Mich.

No Drawing. Continuation-impart of abandoned application Ser. No. 185,893, Oct. 1, 1971. This application Feb. 23, 1973, Ser. No. 335,379

Int. Cl. C08g 45/06; B32b 2.7/38; B32b 27/04 US. Cl. 161-88 6 Claims ABSTRACT OF THE DISCLOSURE Mixtures of the diglycidyl ethers of a bisphenol such as bisphenol A and a diglycidyl ether of an aliphatic polyhydroxyl containing compound such as the diglycidyl ether of neopentyl glycol are modified with hydrogen sulfide to produce epoxy resins which when cured with an aminated polyglycol are useful in the preparation of flexible laminates.

This application is a continuation-in-part of our c0- pending application Ser. No. 185,893, filed Oct. 1, 1971, now abandoned.

This invention relates to new epoxy resin compositions, cured products and flexible laminates prepared therefrom.

Background of the Invention The flexible electrical laminate industry is a relatively new art. Until a few years ago, the ,4 inch hardboard had been the standard product in the electrical laminate field. In the last two to five years, a tremendous technicological boom has occurred with the advent of the ultrathin and multilayer board. The advantages of flexible circuitry include great savings in space, weight, and cost of assembly.

Relatively few materials are available which are suitable for use in flexible laminates. In general, three material types have been used for most flexible circuit device fabrication; PEP (polymers of fluorinated ethylene such as Teflon or fluorinated propylene copolymers thereof, polyester film (Mylar), and polyimide (Kapton) fihn. These are all unreinforced films. There is a need for reinforced films also. The industry is looking for a flexible epoxy resin/hardner system to be impregnated in a suitable substrate such as glass cloth, Reemay (spun Mylar), Nomex nylon paper, etc. In the case of PEP substrates, copper is heat bonded directly to the film without cladding adhesives. However, the thermal stability is bad with PEP. The 520 F. soldering temperature approaches the melting point of PEP. During soldering, complete loss of copper adhesion can occur as well as physical distortion of the circuitry device. Other FEP disadvantages include cold flows and low tensile strength. FEP advantages include excellent electrical properties, flame retardancy and good peel strength.

Polyester film substrates are metal cladded using a cladding adhesive. Excessive heat during soldering (520 F.) can cause film disorientation with a resultant loss of desirable properties. Mylar degrades at 425 F. When polyester film is dipped in molten solder, it immediately melts. Another disadvantage besides the poor thermal stability is the minimal copper peel strength. Advantages include toughness, good electrical properties, good solvent and water resistance, and good flexibility.

At the present, no one is able to pass the rigorous thermal stability requirement except through the use of high priced polyimide (Kapton). Kapton film costs around $25.00 per pound.

3,829,354 Patented Aug. 13, 1914 The compositions of the present invention when cured with a polyglycol diamine give very good flexible laminate properties. Reemay (spun Mylar), glass, or Nomex nylon paper can be impregnated with the above formulation to give good properties.

Epoxy resins have been modified previously by reaction with hydrogen sulfide as taught in US. 2,633,458; however the epoxy resin compositions of the present invention have not previously been prepared. It is these hydrogen sulfide modified epoxy resin compositions of the present invention that make the flexible epoxy resin electrical laminates of the present invention possible. The examples herein will demonstrate that laminates prepared from the hydrogen sulfide modified epoxyresins of the prior art possess certain deficiencies such as one or more of the following, not readily capable of being B-staged, poor flexibility, delamination, and failure of a crease test hereinafter described.

Detailed Description of the Invention The epoxy resin compositions of the present invention comprise the reaction product of hydrogen sulfide with an epoxy resin mixture comprising (A) from about 40 to about 85 percent and preferably from about 50 to about percent by weight based upon the combined weights of A and B of an epoxy resin represented by the general formulae "ice wherein each Y is independently a divalent hydrocarbon radical having from about 1 to about 6 carbon atoms,

each R is independently hydrogen, methyl or ethyl, each R is independently hydrogen or an alkyl group having from 1 to about 4 carbon atoms, m 'has an average value of from about 0.01 to about 2, and n has an average value of from about 0 to about 0.2.

(B) from about 15 to about 60 percent and preferably from about 25 to about 50 percent byweight based upon the combined weights of A and B of the diglycidyl ether of an aliphatic polyhydroxyl containing compound When catalytic type curing agents such as tertiary amines and Lewis acids are employed, they are employed in quantities of from about 2 parts to about parts and preferably from about 3 parts to about 8 parts per 100 at temperatures of from about 110 to about 170 C. for from about to about 60 minutes and preferably at about 120 to about 150 C. for from about 30 to about 45 minutes.

parts by weight of Component (A). 5 Other materials may be added to the com ositions as P Suitable aminated polyglycols which may be employed desired and include fillers such as for example, calcium in the present invention include, for example, those comcarbonate, aluminum powder, silica, asbestos, mica, diapounds represented by the following formula including tomaceous earth, and the like; accelerators such as, for mixtures thereof. 10 example, phenols, BE, complexes, organic acids and anhydrides, and the like. The following examples are illustrative of the present invention and are not to be construed as limiting the scope HaN CH|CHO- CH=CHNHa 15 thereof any manner- In each of the examples, the epoxy resin or mixture of n u o epoxy resins together with 0.05 percent by Weight based upon the weight of the epoxy resin or epoxy resin mixture of ethyltriphenylphosphonium acetate-acetic acid complex Each R is independently methyl or ethyl and wherein )1 Catalyst was added to asuitable reaction vessel. After heathas an average value of from about 2 to about 16 and mg to about 130 C., the indicated quantities of hydrogen preferably from about to about sulfide was bubbled into the vessel at the rate of about These aminated polyglyools may be Prepared by the 25 0.25 l./m-inute. The vessel was their purged with nitrogen procedures given in the patents U.S. 3,236,895 and French for about mmutes at abfmt 130 The contents were 1,547,228 which are incorporated herein by roferonco then cooled and the physical propertles of the resultant The above compositions may be 38mg, partially product obtained. The results are reported in Table I. cured, to a tacky but self-releasable condition. This is 30 Each 9 the resms Prepared as shown In Table I were advantageous in that metal clad laminates can be prepared mlxed wlth a amme and R'eemay cloth (Spun by applying a sheet of metal to the B-staged resin and then Mylafi) dlPPed Into formulatlon and eured m an completing the cure without the necessity of applying presoven at for f e resultant lammafes Sure to the laminate as is required in tho laminates were sub ected to flexibility, tear resistance, water resistploying Mylar, fiberglass, Nomex and the like. B-sta in a ce and crease tests. The results are reported in Table II. is a characteristic that is desirable by the flexible laminate Addmonal Samples of g cloth dlPPed Into each of the resin-polyglycol amine mixtures were B-staged by industry. a

The above compositions may be B staged by heating heating at about 120 C. for about 12 minutes after which at tem eratures of from about to about 170 C for a mil thick copper Sheet was toned onto B-staged p b 0 t d f M f Reemay cloth by means of rubber rollers and then placed from about 4 out 3 es an pre era y or in an oven, without any outside pressure, and cured at 1 about to about for from about 6 to 45 about 120 C. for about 15 minutes. Each sample was about 12 mmutes subjected to copper peel strength and a 530 F. Solder The B-staged resins may be completely cured by heating Test The results are reported in Table TABLE I1.

Comparative examples F G H I J Example 11 15.11/ E.B 4H E.C169 E.D Ex.E/22'i Ex.12l.4. i aifii'y filsfiifi fifi mms APO: 1/12 APG i/12 1564/12 fi'Gi/m APG 1/ APG/1/12. Percent resin in Reemay substrate-.. ND. 82. 71.8. .0. N.D.. 75.2. Flexibility l N.T. Very poor N.T Excellent N.T Excellent. Tear resistance N.T 11.0, N.T 3.8, 3.4-. N.T 5.0, 4.3. Crease test N.T F il N.T Passed. N.T Passed. Water resistance after 24 hrs. N.T 1 R N.T 3.1-.-. N.T 3.0. Copper peel strength, lbs. lin." Reign} didpot 8.2 Relsi igiid not 5 5 B23 51; 5iigig ot 5.0.

' 'S 8 B. e, 530 F. solder test, 20 sec. f Failed (partial .i Failed (total Passed (not gelglrgliirgtion delamination.) affected).

Exmnnln 12 13 14 15 16 17 E .2249 Ex. 3/53 Ex. 4/251; Ex. 5/27 Ex. 6/291 Ex. 7 30. i iic2fl$1ff7 ms A PG 1/12 APG 1/12 APG 1/12 APG 1/12 APG 1/12 APG 2/10.2. Percent resin in Reemay fll'lhlflfltfl 79.5.. 85 0. 80. 84.9. 82.4. N.D. Fl ibilit 1 fiEgnglgnnt gj'osllnnf 3'Egvggnnt gignzllanf 0 ifigxcellent,

I r s e i t i Pa sad Passed Passed Pass Pass Passed. Water resistance after 24 hrs. 2.7 3.1- 3.3-. 2.9- 1.9.. N.T. Copper peel strength, lbs.lin. 10.7.. 9.2. 3.9- Gggdgglohesive 3.9 10.

f ure). d, P d, t P d, t P d, t P ss (1, not Passed, not 530 F Solder test 20 sec g cte i g ete de a cte d? a cte d? ifi cted. afl'ected.

See footnotes at end 01! table.

TABLE II-Continued Exam nla 18 19 20 21 22 23 Epoxy resin, type/gms. Ex. 7/30 Ex. /27 Ex. 8/22.- Polyglycol amine, type/gms. APG 3/8.1 APG 5/10- APG 1/12 Percent resin in Reemay sub N. N.D N.D 84.5- Flexibility 1 Good.-- Excellent Excellent...- Excellent. Tear resistance 1 4.7 6 5 7 Crease test a Passed. Water resistance after 24 hrs. N. Copper peel strength, lbs/in. 8 Good (cohesive copper failure). F. solder test, sec." Passed, not Passed, not Passed, not Passed, not Passed, not Passed, not

afiected. affected. afiected. afiected. afiected. afiected.

i fi xllflgeffi-minatmn of flexibility oi composite-Flexibility was determined by visual observation while bending the specimens. Samples were rated u e y as:

Excellent=Easily bent without resistance.

Good=Easily bent with slight resistance.

Fair=Easily bent with moderate resistance.

Poor=Sample very resistant to bending.

Very Poor= Sample very rigid. Sample would crack before bending.

I Tear resistance of composite.-ASTM D 1004 was used. 1

t H(;Jreaseest.The composite was creased over back and forth 10 times. It was noted if the specimen cracked or not. If it cracked, it failed, if it did no passe 4 Water resistance test-1 x 3" strips of the composite were weighed on an analytical balance. The specimens were placed in distilled water at 25 C. for 24 hours. The samples were dried and reweighed. The amount of water absorption should be less than 5%.

5 Copper peel strength test.-1 x 4" metal strips were treated with cleaning solution for minutes to form a rough surface for adhesion purposes. Then a 1" x 4 copper-clad composite strip was glued to the metal strip using a conventional adhesive. A 1" section oicopper was peeled away from the Reemay substrate at an angle of 90. By use of an Instron machine, the 90 force required to peel the copper off was measured.

1 520 F. solder bath test-The copper-clad laminate was dipped in a520 F. solder bath for 20 seconds. It was noted it the sample delaminated or blistered. If delamination or blistering occurred, the specimen failed this test.

1 N.T.=Sample not tested.

3 N .D.=Not determined.

Sample had insuificient reactivity and/or too low viscosity to make B-staging feasible. The substrates were too resin lean to give adhesion to copper foil. The resin/hardner mix ran ofl the substrate before it cured.

IDENTIFICATION OF MATERIALS 30 (4) APG 1 is an aminatcd polypropylene glycol having an amine hydrogen equivalent weight of about 120 and an average molecular Welght of about equivalent ratios below about 0.20:1' do not result in APG 2 is an aminated polypropylene glycol having an amine hydrogen equivalent weight of about 102 and an 5 average molecular weight of about 250.

APG 3 is an aminated tripropylene glycol having an amine compositions which possess the desirable characteristic of B-stage capability, see Comparative Examples C and H.

hydrogen equivalent weight of about 81 and an average (5) molecular weight of about 190. HZSZHZC CH+ APG 4 is an aminatcd polypropylene glycol having an 40 amine equivalent Weight of abcfut j a equivalent ratios above about 0.70:1 do not result in g y g g g'i giigf g fig gg gg gfig 323 2;}? flexible laminates which pass the Solder Test, see Comrom c e s 1 I APG 5 is an aminated polypropylene glycol having an Paratlv? Examples D and amine hydrogen equivalent weight of about 100 and a We molecular Weight of about 400 commercially available A flexlble laimlnate Comp? g a Spun, Woveflfl f o J ffer Ch i Company as j ff mj 400 reinforcing media selected from the group consisting of D.E.R. 331 is the diglycidyl ether of bisphenolAhaving fiber glass, yl y potion, and polyester, d a an average cpoxidc equivalent weight of about 187-189 cured composltlon p g commercially available from The Dow Chemical Comall P Y Tesln comPosltlon Q p f the feactli'm pany, product of hydrogen sulfide with a mlxture compris- DGEN'PG is the diglycidyl ether of neopentylglycol having 8 an avg. epoxide equivalent weight of about 130. from about 40 to about P13rcent y Weight DGEG is the diglycidyl ether of glyccrine having an averbased p b combined Welghis A a d B o age epoxide equivalent weight of about 153. an P Y resin represented y the general DGE'BD is the diglycidyl other of 1,4-butanediol having 11111136 an average epoxidc equivalent Weight of about 134. ENR is a phenol-formaldehyde based epoxy novolac resin 0 having an average epoxide equivalent weight of about 166 and an average functionality of about 2.1. I-

The preceding examples in addition to exemplifying OH the present invention demonstrate that: o (1) diglycidyl ethers of aromatic hydroxyl containing CHPO Y K compounds alone do not produce laminates which pass and the Crease Test and Solder Test, see Comparative Examples B and G;

(2) diglycidyl ethers of aliphatic hydroxyl containing 0 0 compounds do not possess the desirable characteristic of B-stage capability, see Comparative Examples A 0-CI-h-CH-CH; 0GH1-C GH: O-GHHJ -CH2 and F.

(3) quantities of the diglycidyl ether of an aromatic hy- I' "I droxyl containing compound (Component A) below 5 about 40% do not possess the desirable characteristic LI J R! In R] of B-stage capability, see Comparative Examples E and J. R1

9 wherein Y is a divalent hydrocarbon radical,

0 0 II I H SS, S, or O-,

each R is independently hydrogen, methyl or ethyl, each R is independently hydrogen or an alkyl group having from 1 to about 4 carbon atoms, In has an average value of from about 0.01 to about 2, and n has an average value of from about 0 to about 0.2, and

(B) from about 15 to about 60 percent by weight based upon the combined weights of A and B of an aliphatic polyhydroxyl containing compound selected from the group consisting of a diglycidyl ether of neopentyl glycol, a diglycidyl ether of glycerin and those represented by the formulae wherein x has a value of from 1 to about 5,

wherein each R is independently methyl or ethyl and m has an average value of from about 1 to about 25, preferably from about 1 to about wherein the quantity of hydrogen sulfide employed is that which will provide an 10 ratio of from about 0.20:1 to about 0.70:1; and (2) an aminated polyglycol represented by the general formulae It I i wherein each R is independently methyl or ethyl and wherein n has an average value of from about 2 to about 16. 2. The flexible laminate of Claim 1 wherein the Hzs 2H3C-CH- ratio is from about 0.25:1 to about 0.60:1.

3. The flexible laminate of Claim 2 wherein the epoxy resin component (A) is a diglycidyl ether of bisphenol A and the epoxy resin component B is a diglycidyl ether of neopentyl glycol.

4. The flexible laminate of Claim 3 wherein the reinforcing media is spun polyethylene terephthalate.

5. The flexible laminate of Claim 4 additionally clad with a metal.

6. The flexible laminate of Claim 5 wherein the metal is copper.

References Cited UNITED STATES PATENTS 2,633,458 3/1953 'Shokal 260-837 3,236,895 2/1966 Lee et a1 2602 XR 3,355,512 11/1967 De Acetis et al. 26047 XR GEORGE F. LESMES, Primary Examiner C. E. LIPS'EY, Assistant Examiner US. Cl. X.R.

117126 GE, 138.8 F, 138.8 N, R, 143 A, 145, 161 ZB; 16l92, 93, 150, 184, 185, 186, 192, 213, 227, 231, DIG. 4, DIG. 7; 26037 EP, 830 TW 

